How to enable or disable automatic updates for Passbook cards

Many different Passbook cards auto-update on their own without requiring you to do anything: Your balance will refresh on your Starbucks card, and if your gate changes at the airport, Passbook will alert you appropriately. If a pass isn't automatically updating, however, or you'd rather manually manage updating your cards, you can easily turn the automatic update feature on and off on a card-by-card basis.